18-IN. MINIMUM
TO BURNERS
Fig. 16--1nstNtation in a Garage
A93044
F[ RNA(E CORROSION HAZARD
Air _br con_bustion must not be contaminated by halogen
compounds, which include fluoride, chloride, bromide, and
iodide. These elements could corrode heat exchangers and
shorten fhmace life. Air contaminants are found in aerosol
sprays, detergents, bleaches, cleaning solvents, salts, air
fresheners, and other household products.
The following types of fl_mace installations may require OUT°
DOOR AIR fbr combustion due to chemical exposures:
° Commercial buildings
° Buildings with indoor pools
° LaundQ- rooms
* Hobby or craft rooms, and
* Chemical storage areas
If air is exposed to the fbllowing substances, it should not be used
for combustion air, and outdoor air may be required _br eombus°
tion:
Permanent wave solutions
Chlorinated waxes and cleaners
Chlorine based swimming pool chemicals
Water sokening chemicals
Deqcing salts or chemicals
Carbon tetrachloride
Halogen type refrigerants
Cleaning solvents (such as perchloroethylene)
Printing inks, paint removers, varnishes, etc.
Hydrochloric acid
Cements and glues
Antistatic _hbric softeners _br clothes dQ'ers
Masonry acid washing materials
All fuel=burning equipment must be supplied with air fbr Net
combustion. Sufficient air must be provided to avoid negative
pressure in the equipment room or space. A positive seal must be
made between the Nmace cabinet and the returnoair duct to
prevent pulling air fi'om the burner area and from &aft safeguard
opening.
CARBON MONOXIDE POISONING HAZARD
The operation of exhaust fans, kitchen ventilation _ms,
clothes &yers, attic exhaust fans or fireplaces could create a
NEGATIVE PRESSURE (ONDITION at the furnace.
Make-up air MUST be provided for the ventilation devices, in
addition to that required by the fl/rnace. Refer to the (arbon
Monoxide Poisoning Hazard warning in the venting section
of these instructions to determine if an adequate amount of
make=up air is available.
The requirements for combustion and ventilation air depend upon
whether or not the fl/mace is located in a space having a volmne
of at least 50 cubic feet per 1,000 Bmh input rating ibr all gas
appliances installed in the space.
Spaces having less d-_an 50 cubic feet per 1,000 Bmh require
the O[ TDOOR (OMB[ STION AIR METHOD.
Spaces having at least 50 cubic feet per 1,000 Btuh may use the
INDOOR ( OMBUSTION AIR, STANDARD or KNOWN-
AIR INFILTRATION METHOD.
Outdoor (ombustion Air Method
1. Provide the space with sufficient air %r proper congbustion,
ventilation, and dilution of flue gases using pem_anent hori-
zontal or vertical duct(s) or opening(s) directly comnmnicat-
ing with the outdoors or spaces that freely communicate with
the outdoors
2_
Fig. 17 illustrates how to provide TWO OUTDOOR OPEN-
INGS, one inlet and one outlet combustion and ventilation air
openings to the outdoors.
a. One opening MUST commence within 12" (300 mm) of
the ceiling and the second opening MUST commence
within 12" (300 mm) of the floor.
b. Size openings and ducts per Fig. 17 and Table 1.
c. TWO HORIZONTAL DUCTS require 1 square inch of
free area per 2,000 Btuh (1,100 mm2ikW) of combined
input fi_r all gas appliances in the space per Fig. 17 and
Table 1.
d_
TWO OPEND._GS OR VERTI(AL DUCTS require 1
square inch of flee area per 4,000 Btuh (550 ram2 kW) _br
combined input of all gas appliances in the space per Fig.
17 and Table 1
3. ONE OUTDOOR OPENING requires:
a. 1 square inch of flee area per 3,000 Btnh (734 n'lnl2ikW)
for combined input of all gas appliances in the space per
Table 1 and
b. Not tess than the sum of the areas of all vent connectors in
the space
The opening shall commence within 12" (300 mm) of the
ceiling. Appliances in the space shall have clearances of at
least 1" (25 ram) from the sides and back and 6" (150 mm)
fiom the front. The opening shall directly communicate
with the outdoors or shall communicate through a vertical
or horizontal duct to the outdoors or spaces (crawl or attic)
that fl-eely communicate with the outdoors.
Indoor Combustion Air_) NFPA & AGA
Standard and Known-Air-InfiRration Rate Methods
Indoor air is permitted %r combustion, ventilation, and dilution,
if the Slandard or Known-Air-InfiRration Method is used
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